Process for disintegrating and devulcanizing rubber scrap



Patented June 19, 1934 UNHTED 'CSTATES PROCESS FOR DISINTEGRATING ANDDEVULCAN IZIN G RUBBER SCRAP Russell R. Gross, Akron, Ohio, assignor toThe Xyios Rubber Company, Akron,

ration of Ohio Ohio, a corpo- No Drawing. Application May 31, 1930,

Serial No. 458,922

8 Claims.

This invention relates to a process for reclaiming rubber scrap bydisintegration and devulcanization.

The commercial method of reclaiming rubber from scrap as almostuniversally practiced, comprises digesting the scrap, to which a smallamount of oil or tar is added, with a caustic soda solution at atemperature of approximately 365 Fahrenheit and a pressure of 175 poundsper square inch for a period of from five to thirty hours, then Washing,(sometimes treating with acid and washing again) drying, straining,milling and refining. This process results in a loss of all of thetextile fiber and a portion of the rubber, in addition to the otherdisadvantages of long duration of treatment, cost of power, water andchemicals and the problem of disposal of the waste liquors.

Again, it has been suggested that the rubber to be reclaimed besubjected to the action of a swelling agent having a low boiling pointsuch as carbon-bisulphide, acetone, benzene or the like. The swellingagent and the rubber are brought together under heat and pressure inclosed container in which the pressure is suddenly released to furthersponge and explode the rubber after which any fiber is removed bystraining, floating or other processes. This method requires the use ofexpensive swelling agents which must be recovered to make the processpractical. It is comparatively slow and necessitates expensiveequipment.

The general purpose of the invention is to overcome the difliculties anddisadvantages of the prior art by .the provision of a rapid,inexpensive, and efficient method for reclaiming rubber.

It is also an object of the invention to devise a method which isadapted to reclaim or devul- .canize rubber scrap of all types includingthat with textile fibers therein, such as tire carcasses and thatwithout fibers therein, such as solid tires, air bags, tubes and thelike.

Another object resides in providing a method 'S which eliminates the useof expensive chemical agents.

A further object of the invention is the provision of a process forreclaiming rubber with textile fibers therein by which method the re- Ticlaimed rubber retains substantially all the textile fibers therein butin such a comminuted, distributed condition that the reclaimed rubbercan be milled, compounded and handled in a manner similar to the stockcontaining no textile fibers.

The above and other objects of the invention are achieved by the methodherein described,

it being understood that the invention is not limited to the exactprocedure described. This application is a continuation in part of mycopending application Serial-No. 222,951 filed Sep- 60 tember 29, 1927.

According to the present invention the rubber scrap is first broken upby a hogger or other means, preferably to such a size that the pieceswill pass through approximately a one-half inch 5 screen. It will beunderstood that scrap of all types or from all sources is not as a rulemixed together but that all solid tire scrap is kept and handledtogether, all pneumatic tire scrap handled together, etc. In varioussources demands somewhat varied treatment particularly as to length oftreating time as hereafter more fully explained.

After the rubber scrap has been broken up into small particles, asuitable batch thereof is subjected to steam at a substantialtemperature and pressure for a predetermined time. The size of the batchis determined by the handlingapparatus which is in the form of a closedchamber.

After the determined treating time has'elapsed 0 the pressure issuddenly released from the batch in any known manner. The pressurerelease is ordinarily accomplished by removing a cap or plug from anorifice in the closure mentioned above so that the pressure release willblow the 5 material out through the orifice and into any suitable devicefor separating the steam from the product, such as a cyclone separator.

subjecting the rubber batch to steam in this manner will cause the steamto penetrate into the 0 rubber particles so that when the pressure issuddenly released the particles are exploded or disintegrated by thesteam pressure within the particles. The resulting rubber batch is agummy, soft mass of minute disintegrated particles which 95 aftermilling and refining can be readily compounded. In using the processwith scrap containing textile fibers, it has been found that Whilecertain of the fibers are somewhat charred, that the fibers have as awhole been substantially 1' hydrolyzed and disintegrated so that aftermilling and refining the devulcanized batch, the fibers have worked intothe rubber as a filler and have substantially disappeared.

In practicing the invention, pressures ranging 5 from 300 to 1000 poundsper square inch and temperatures of 400 to 600 Fahrenheit have beensuccessfully used. The time the scrap is subjected to the steam underpressure varies from 1 to 30 minutes or more and is dependent upon theother words scrap from the Inner tube scrap 2 minutes at 400# sq. in.at.

Pneumatic tire scrap 5 minutes at 500#/sq. in. at 470 F.

Solid tire scrap 15 minutes at 600#/sq. in. at 489 F.

While the preferred procedure contemplates the coaction only of the livesteam and rubber scrap,

it is to be understood that additional reagents including softening,swelling and devulcanizing agents may obviously be employed therewith.

The invention also contemplates preheating the batch when it isinitially placed in the container. This will cover a short period offrom 1 to 10 minutes using low pressure steam in the neighborhood of 150to 300 pounds per square inch.

Various modifications of the invention can be resorted to withoutdeparting from the spirit of the invention or the scope of the appendedclaims.

What is claimed is:

1. The process of distintegrating and devulcanizing rubber scrap whichcomprises the steps of breaking the scrap into relatively small pieces,charging the scrap into a closed container, introducing and maintaininglive steam at a relatively .1 low temperature and pressure in thecontainer in direct contact with the scrap to preheat the scrap,introducing and maintaining live steam at a relatively high temperatureand pressure in the containerfor a determinate time and suddenlyreleasing the pressure in the container whereby the rubber scrap isdisintegrated and devulcanized.

2. The process of disintegrating and devulcanizing rubber scrap whichcomprises the steps 2 1 of breaking the scrap into relatively smallpieces,

charging the scrap into a closed container, introducing and maintaininglive steam at a relatively high temperature and pressure in thecontainer pounds per square inch, and suddenly releasing the pressure.

'4. The process of reclaiming rubber scrap which consists in subjectingthe scrap tothe action of live steam at a temperature in excess of 266Fahrenheit and at a pressure of approximately 600 pounds per squareinch, and suddenly releasing the pressure.

5. The process of reclaiming rubber scrap which consists in subjectingthe scrap to the action of live high pressure steam at temperaturesbetween 400 and 600 degrees Fahrenheit, and suddenly releasing thepressure.

6. The process of reclaiming rubber scrap which consists in subjectingthe scrap to the action of live high pressure steam at a temperature ofapproximately 490 degrees Fahrenheit and suddenly releasing thepressure.

'7. The process of disintegrating and devulcanizing rubber scrapcontaining cotton cords or fabric, which comprises the steps of chargingthe scrap into a closed container, introducing live steam at atemperature in excess of 266 Fahrenheit and at pressures in excess of300 pounds per square inch into the chamber in direct contact with thescrap, and suddenly discharging the contents of the container wherebythe action of the high pressure, live steam and the sudden dischargechemically change and disintegrate the cotton and rubber.

8. The process of reclaiming rubber scrap, which comprises subjectingthe scrap to the action of live steam at a relatively high pressurecompared to pressures used in the devulcanization of rubber by thedigesting process, and suddenly releasing the pressure whereby the steamabsorbed into the material is suddenly expanded, "f

RUSSELL R. GROSS.

